Material cutting and printing system

ABSTRACT

A cloth cutting system wherein cloth is carried in a single layer into a cutting area wherein a laser beam is focused on the cloth and is directed by computer commands to travel within the cutting area so as to cut a plurality of patterns through the cloth rapidly and accurately.

Mason et a1.

1451 Sept. 25, 1973 MATERIAL CUTTING AND PRINTING 3,548,502 12/1970 Baldwin 83/925 CC SYSTEM 3,610,081 /1971 Gerber 83/925 CC 3,548,699 12/1970 Gerber 83/925 CC 1 t s: Wi iam 1- Mason, WeStlflke g 3,422,246 1/1969 Wetzel 214/121 1. Douglas W. Wilson, Paclfic Pal1- 3,369,101 2/1968 Di Curcio 214/121 L sades; Dou 135 M. Considine 3,391,342 7/1968 Doyle 340/1725 f ffif' l y'g a FOREIGN PATENTS OR APPLICATIONS 11 a e, 1m1, V I w 993,705 6/1965 Great Britain 214/121 L [73] Assignee: Hughes Aircraft Company, Culver PUEHJCATIONS City, Calif llfiier Cuts a Fme Figure Washmgton Post March 9, [22] Filed; 1972 The Carbon Dioxide Laser Design Engineering May 1211 Appl. No.: 219,007 1969 PP Primary Examiner-R. F. Staubly 219/121 83/925 Assistant ExaminerGeorge A. Montanye A w H M n t at l [58] Field of Search 214/121 L, 121 EB; omey ac 1S er a 235/151.11; 340/1725; 444/1; 83/71, 925 CC [57] ABSTRACT 56] References Cited A cloth cutting system wherein cloth is carried in a sin- UNITED STATES PATENTS gle layer into a cuttmg area yvherem a laser beam is fo- 3 226 527 H1965 H d, cused on the cloth and 1s chrected by computer com- 3597578 8/1971 mg t mancls to travel within the cutting area so as to cut a 36]4369 10/1971 J ss; et a 21412 L plurality of patterns through the cloth rapidly and accu- 3,612,814 10/1971 HOUldClOfI 214 121 1. ram)" Claims, 15 Drawing Figures 4| Control Panel 4 27 37 3| 33 19 l l 23 1 1 P loser [Qatgqlol osiiioning ower on mg 0 Bop; l CDlgliGl gem/(mics Supply Electromcs ec ompuier J i, W 9 I'- '1 l l l l l l 1 I e g o 5 0) Y l 5 2 l 5 a l l Z' I I 2w 1, L Cutting Areo :8 I J X PATENTEI] SEPZ 5 I975 SHEET 02 [1F 10 Fig. 8.

PATENTEDSEP25 I915 3.761.675

saw us or 10 PATENIEUSEPZSIQH sum as or 10 PATENTEDSEP25|975 3 .7s1'.s75

sum '09 or 10 XDDA 277 V x AXIS R REGISTER Z c t COMMANDS cos a FROM COMPUTER cos a 265Y AX 5 x DIRECTION F I (TO COMMAND coMPuTE I22 COUNTER- 269 INPUT CONTROL) DOWN COUNT Ax COUNTER ZERO ZERO 9 DETECTOR DETECTOR EE L u.

(ALL REGISTERS) g DWELL E ENABLE FEEDRATE t GENERATOR M BL0cK LOAD 30 kHz 30 kHz MAX DWELL DOWN TO COMPUTER RATE COUNTER 283 ZERO DWELL DETECTOR TIME FROM M COMPUTER I22 DOWN A A Y M COUNTER coum FROM COMPUTER I22 l I :v DIRECTION (T0 COMMAND 265x COUNTER- lNPUT CONTROL) SIN 9 FROM COMPUTER 1 c v AXIS n REGISTER E COMMANDS to Fig. 15.

L J Y DDA 277 Crossarm Controllers PATfNTEnsl-irzsmn 761 4,675

' POSITION F DBA RESOLVERS T R I I' "E IE; .r-

' Y TOALL I TDATRRDSSAR c0MMAND FTANGELE EE I l J I I coMM CO I EXTENDED AXIS MM RANGE V0 AMP 3 NT TROL COUN I PHASE I AND MOTOR I LOGIC DISCRIMINATOR I CONTROL I I 3T3 297 I39 I X AXIS 2 5 I POSITION 1 COMMANDS J SENSOR SENSOR AMPLIFI MOTION CONTROL MOT TROL RESET INTEGRATOR MOTIO I I I UT T TROL CLOCK BLE T--T-T-T-T--: I I I I COMMAND EXTE D XAXIS RAN v0 AMP NTER COMMAND T COUNTER 55 MO LOGI x DISC INATOR CONTR I I M I- WIS 309 307 313 POSITION S T ANGLE COMMANDS x AXIS CONTROL, PHASE TYPICAL, 3 PLACES ANGLE CONVERTER 295 I 293 I J T REF.VOLTAGE NTROL CLOCK I l I I l I I 297 COMMAND I EXTENDED AXIS I I COUN COMMAND 3 GE I I ve AMP CONT COUNTER 7 SE AND MO I LOGIC I DISCRIMINATOR CONTRO I I I L YAXIS 309 307 I 313 3H I I I SHAFT ANGLE v AXIS CONTROL TO PHASE- I TYPICAL, 4 PLACES ANGLE 295 293 CONVERTER 1 MATERIAL CUTTING AND PRINTING SYSTEM CROSS REFERENCES TO RELATED APPLICATIONS LASER CUTTING SURFACE, U.S. Pat. application Ser. No. 3,665 filed by Robert M. Zoot on Oct. 8, 1971 as a continuation of pending prior application filed on Jan. 19, 1970, discloses a honeycomb surface for supporting material being cut by a laser beam without refleeting the beam back at the material.

Howard R. Friedrich, U.S. Pat. application Ser. No. 3,627 for a LASER LENS COOLING SYSTEM filed Jan. 19, 1970, now U.S. Pat'. No. 3,696,230, discloses a system wherein a stream of gas is used to cool a laser beam focusing lens and also for controlling combustion of the material being cut.

An improved working surface featuring knife-edged supports is the subject of U.S. Pat. application Ser. No. 218,896 filed by Georgette S. Egan on a WORKING SURFACE FOR RADIANT ENERGY BEAM CUT- TER concurrently herewith.

A system whereby a laser beam is movable on a selected surface without moving the beamssource is the subject of U.S. Pat. application Ser. No. 219,007 filed by Robert M. Zoot and Douglas W. Wilson on a LASER CUTTER OPTICAL SYSTEM concurrently herewith.

MATERIAL HOLDING AND SMOKE REMOVAL SYSTEM FOR A LASER CUTTER, U.S. Pat. application Ser. No. 184,139, filed on Sept. 27, 1971 by Rodolfo Castro and Esteban J. Toscano, discloses a system for both holding in place fabric being cut and for removal of combustion by-products from the cutting area both above and below the cloth. I

CONVEYOR ADVANCING SYSTEM, U.S. Pat. application Ser. No. 218,933, filed concurrently herewith, by Robert L. I-lasslinger, William J. Newton, Esteban J. Toscano and Rodolfo Castro discloses a system for compensating positioning errors in a conveyor upon which material to be cut may be carried.

A system for controlling combustion of material being cut by a laser beam and for keeping debris out of a laser focusing system is the subject of US. Pat. application Ser. No. 202,422 filed on ENVIRONMENTAL CONTROL AT LASER CUTTING POINT by Rodolfo Castro, William 3. Newton and Esteban J. Toscano on Nov. 26, 1971.

TENSION FREE CLOTH DISPENSING APPARA- TUS, U.S. Pat application Ser. No. 157,247 filed on June 28, 1971 by Rodolfo Castro, William J. Newton and Esteban J. Toscano discloses a system for dispensing fabric from a roll onto a conveyor without stretching the fabric.

A particularly advantageous method of allocating work to cutters used in the system claimed in the present application, while also disclosed herein, is separately claimed by Robert L. Hasslinger in WORK- LOAD ALLOCATION FORONE OR MORE TOOLS, U.S. Pat. application Ser. No. 218,958 filed concurrently herewith. All of the foregoing are incorporated herein by reference, are U.S. applications and are assigned to the assignee of the present application.

BACKGROUND OF THE INVENTION The present invention relates generally to a system and a method for cutting parts froma layer of material by severing the material according to preselected,

stored patterns,and optionally marking the cut parts in accordance with stored information. Cutting and severing are used interchangeably, herein, both denoting the separation of the cut 'or severed material along the cutting or severing path.

The principal methods for cutting patterns of fabric for mass producing apparel is to stack the fabric many layers high and to make the cuts manually by means of a mechanical cutting device along the perimeters of wooden forms laid out on top of the stack. Even where the cutting operation is automated, as for example by means of an oscillating blade guided by means of numerical commands, the inherent speed limitations of the blade require stackingof the fabric for efficient operation. Multi-layer cutting, although efficient, has several disadvantages. First, it requires that the material be cut'for a large numberof suits of the same size and shape at the same time. As a result, the manufacturer must eitherwait until he has accumulated enough ordersfor-a large run or hewill have to maintain a large inventory.

Secondly, the cut pieces are usually not identical because of deviations in the cut between layers, particularlybetwe'en those near the top and the bottom of the stack. This makes the sewing process more difficult and can in some instances affect the ultimate appearance of the garment.

Moreover, since cutting accuracy is limited, individual patterns must be spaced relatively far apart to prevent overlap. Yet another drawback of the multi-layer cutting is caused by Slight variations in the color of the fabric. Thus, in order to insure that all the pieces making up a given garment have the same color, it is necessary to select all such pieces from the same layer of cloth. This requires that each layer of the stack be separately identified, a time consuming process.

The solution to all of these problems is a cutting process which is fast enough and accurate enough to make it economically practical to cut material in a single layer or one-high.

Cutting of material in a single layer permits the manufacturer to cut the pattern for a single garment as soon as he receives an order for it. Thus, he can give fast service without assuming the burden of a large inventory, with its concomitant risk of obsolescence due to rapid changes in styles. Moreover, by numerically controlling the cutting process it can be made accurately repeatable so that each garment will have precisely the same shape as every other garment of the same size and shape. Furthermore, because of the greater accuracy, the different patterns can be more closely spaced, resulting in better material utilization. Yet another advantage of one-high cutting is that it permits patterns to be printed with identifying marks, sewing lines, and other information as an integral part of the pattern cutting process.

OBJECTS OF THE INVENTION At first it would seem like a step backward to cut garment parts singly, part after part, rather than ten or twenty at a time as is being done currently. Certainly the time required to cut each garment would increase by an order of magnitude unless a radically different cutting technique were provided. It is the principal object of the present invention to provide the apparatus and the method which, by virtue of its accuracy and speed will permit the cutting of fabric for a single garment economically.

A related object of the present invention is to provide an apparatus and a method for cutting inherently flammable fabrics with a focused radiant energy beam without igniting the fabric.

Another object of the present invention is to provide a system for cutting sheet material such as cloth with a traveling, cutting focused beam of coherent light while keeping the operator of the system safe, both from the focused beam and from the smoke generated by the cutting process.

A relatd object of the invention is to provide the apparatus and method required accurately to cut the pieces for a plurality of dissimilar garments in rapid succession garment after garment, preferably in response to prerecorded numerical commands.

A further object of this invention is to produce patterns which are marked with sewing information as an integral part of the process of cutting these patterns, and preferably to do so in response to stored digital data.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the invention, material to be cut is laid upon a work support surface which is then moved together with the material lying thereon into a cutting area. Within the cutting area a plurality of spaced apart pieces are cut to preselected patterns from the material by moving a focused radiant energy beam in accordance with numerical commands. Once the cutting is completed, the work support surface with the cut pieces thereon is moved out of the cutting area. In accordance with a feature of the invention the material rests upon an air-permeable work support surface and air is forced to flow away from the underside of that support so as to remove by-products, such as smoke produced by the cutting process.

In accordance with another feature of the invention the cutting beam is a beam of coherent light which is generated by a stationary source, is projected while collimated at, and is focused at the material by, a movable optical device traversed within a cutting area, spaced closely above the material to be cut, and under the control of a digital computer which processes stored signals representing the desired patterns. For maximum cutting speed the laser beam is interrupted under the computers control when the beam is between parts, thus allowing the focusing device to be traversed from the last cut part to the next part to be cut by the shortest route, without regard to passing over material whhch is to form a part.

It is a further optional feature of the present invention that the work support surface also moves through a printing area where the material is stopped next to a printing device. The printing device is operative to mark lines upon the material, either before or after it has been cut, and this marking action is preferably performed in response to numerical commands.

The apparatus and techniques of the present invention achieve their stated objective exceedingly well. Because the laser beam can be turned on and off almost instantaneously and can be traversed extremely rapidly, it is possible to go from pattern to pattern with great speed and the maximum cutting speed of individual patterns is of the order of 40 inches per second on the straight line segments. The speed is controlled to lower values as the tool approaches corners to prevent overshoot and resultant inaccuracy.

The cut produced by the focused laser beam is sharp and narrow, leaving the fabric unfrayed. With manmade materials such as Nylon and Dacron the laser beam also serves to seal the cut edges by melting them during the cutting process. Unlike a mechanical blade the laser beam never dulls, its cut remains uniform, and it is effective in cutting a wide range of materials even those having metallized thread.

BRIEF DESCRIPTION OF THE DRAWINGS Additional objects and advantages of the invention will become apparent from the following detailed description with reference to the drawings in which:

FIG. 1 is a block diagram of an exemplary system in which patterns are cut out of cloth by means of a focused laser beam;

FIG. 2 is an exemplary focusing device which serves to redirect a laser beam from a direction parallel to the material to be cut into a second direction at the material and also to focus the beam;

FIG. 3 is an alternative focusing device for accomplishing the same purpose but using only reflective optics rather than a lens as shown in FIG. 2;

FIG. 4 illustrates the manner in which the smoke generated by the cutting laser beam is removed from above and from below the material which is being cut;

FIG. 5 is a perspective view of the exemplary system including a long conveyor made up of relatively thin slat assemblies, and also showing the carriages for traversing laser beams and printing devices over material lying thereon;

FIG. 6 is a perspective view, partially broken away, of a suitable slat assembly for the conveyor of FIG. 5;

FIG. 7 is a perspective view of a crossarm assembly, of which four are shown in FIG. 5, and which is adapted to traverse a cutting tool or a printing device and in particular the focusing device of FIG. 2 or FIG. 3 over a predetermined work area above the conveyor assemy;

FIG. 8 illustrates a typical pattern cut by means of the system of FIG. 5;

FIG. 9 illustrates an acceptable path approximation which may be made necessary by servomechanism er rors;

FIG. 10 illustrates the location of the work areas in which cutting takes place along the conveyor and the manner in which the workload is distributed between the several cutters;

FIG. 11 illustrates a portion of a marker which includes several patterns laid out so as to waste a minimum of material and cut by means of the apparatus illustrated in FIG. 5;

FIG. 12 is a flow chart which illustrates how the stored digital signals are created for producing a desired marker and how those signals are used to control various parts of the system;

FIG. 13 is a block diagram showing the organization of a computer suitable for driving numerical controls associated with the respective crossarms;

FIG. 14 is a block diagram ofa numerical control for driving the servomechanisms of one of the crossarms in response to signals received from the computer of FIG. 12.

FIG. 15 is a block diagram ofa suitable crossarm servomechanism.

GENERAL DESCRIPTION OF AN EXEMPLARY EMBOIDMENT OF THE INVENTION An exemplary radiant energy cutting system illustrating the principles of the present invention is shown generally in FIG. 1. The radiant energy takes the form of a coherent light beam generated by a laser beam source 11 which is preferably stationary and aimed at a cutting plane within a cutting area 13 by means of a pair of optical devices 14 and 15. In a manner to be described shortly hereinafter, by appropriately moving the optical device 14 and 15 the laser beam produced by the source 11 can be traversed over the cutting area 13 so as to execute any desired route. It will be sufficient to note at this point that the laser beam remains unfocused during the initial portions 11a and 11b of its travel and is focused only in the second optical device 15 so as to become focused in the cutting plane which lies in the cutting area 13.

Material which is to be cut by the focused beam in the cutting area 13 is supported in a single flat layer upon a supporting structure 17 which preferably takes the form of a conveyor. It should be noted that, while the system of the present invention finds its greatest utility and advantage in permitting material to be cut at an economical rate in a single layer, the system could also be usefully employed where more than one layer is to be cut. However, for purposes of the description which follows, operation of the system will always be described with reference to the cutting ofa single layer of material. In the exemplary system, the material from which parts are to be cut is a fabric which is unrolled from a bolt in a single, continuous layer onto the conveyor 17 which is advanced in a series of equal steps so as to carry successive portions of the fabric lying thereon into the cutting area 13. After each advancement of the conveyor 17, parts are cut to patterns from the material lying within the cutting area 13, with the cutting performed being referred to as a bite.

To traverse the focused laser'beam in the cutting area 13 so as to cut out a plurality of separate parts, the optical devices 14 and 15 are moved together in the X direction (parallel to the longitudinal axis of the conveyor 17) and the optical device 15 is moved'relative to the optical device 14 in the Y direction which is at right angles to the X direction. These movements are effected by positioning devices which are moved under the control of a positioning electronic circuit 19 whose principal function is to produce, in response to numerical commands generated by a digital computer 21, electrical'signals compatible with the devices used to move the optical devices 14 and 15. The commands produced by the computer 21 are in turn derived by means of a tape deck 23 from a cutting sequence tape 25 upon which are stored signals which represent the locations and perimeters of the parts which are to be cut from the material in the cuting area 13. Preferably after each part has been cut, the laser beam is interrupted and the beam traversing apparatus which carries the optical devices 14 and 15 is moved to the starting point of the next part at which time the laser beam is re-established.

While interruption of the laser beam could be accomplished by means of a mechanical shutter interposed in the unfocused portion of the beams path, in FIG. 1 a laser power supply 27 is shown to be responsive to the digital computer 21 and to a control panel 29 through lines 31 and 33 respectively. The function of the control panel 29 is to turn on the subsystems such as the computer 21, the positioning electronics 19, the laser power supply 27 and to coordinate them with one another. Thus, for example if, by conventional means such as limit switches or voltage sensors, it is detected that the device for positioning the optical elements 14 and 15 is inoperative, an interlock in the control panel 29 prevents the laser 11 from turning on. Similarly, the control panel 29 will prevent automatic operation of the overall system unless all of the subsystems are operationaL-Additionally, manual commands may be made by means of conventional pushbuttons provdied on the control panel and various indicating lights on the panel apprise the operator of the condition at various points in the system.

Advancement of the conveyor 17 is by means of a conveyor drive 35 such as an electric motor coupled through gears and drive sprockets to a pair of chains by means of which the conveyor 17 is advanced. Operation of the conveyor drive 35 is controlled by a material handling electronics subsystem 37 which is responsive to commands received from the digital computer 21 over a line 39 and'which is also connected to the control panel 29 through a line 41 for the previously stated purpose. Switching of the laser power supply 27 and starting and stoppingof the conveyor drive 35 through the material-handling electronics 37 may be accomplished either in response to command signals recorded on the production tape 25 or in response to command signals which are derived by means. of the digital computer 21 from the information which it receives from the tape 25. Thus, the computer 21 may automatically produce the control signals necessary to operate the laser power supply 27 and the material-handling electronics 37 so that the laser power supply is turned on and off as each part is started and finished, while the material-handling electronics are started and stopped as each complete bite is begun and completed. Also controlled by the material-handling electronics 37 is a material spreader 43 whose function is to dispense the fabric from a bolt in step with the advancement of the conveyor 17 so that the material is deposited on the surfaceof the conveyor without stretching or wrinkling it excessively.

Summarizing this brief description of the exemplary system, the patterns to which parts are to be cut from thefabricbeing advanced by the conveyor 17 are recorded on the cutting sequence tape 25 so that as successive portions of the material are positioned within the cutting area 13, the digital data representing the patterns to which parts are to be cut from those portions are made available to the digital computer 21. The digital computer 21 processes the data associated with the particular portion of material in the cutting area 13 and applies that data in slightly different form, and with additional information generated by the computer, to the positioning electronics 19. The latter, in response, applies control signals to the devices which move the optical devices 14 and 15 soas to traverse the laser beam according to the taped patterns.

Before each part is cut, it is preferable that the laser beam positioning optical elements 14 and 15 be moved so that when the'laser beam is turned on it will be at the starting point of that part. Then the devices 14 and 15 are moved so as to rapidly traverse the laser beam around the perimeter of the part and when the beam has reached the end point of the part, which will typically intersect its starting point, the beam is turned off and the optical devices 14 and are moved to the starting point of the next part to be cut. When all of the parts which are to be cut during a given bite have been completed, the conveyor 17 is advanced so as to bring the next portion of the material into the cutting area 13, the system also being operative at this time to dispense material from the spreader 43 onto the conveyor.

As will be shown in more detailed drawings of the system, it may also include means for marking any of the parts which have been cutout of the material with information that can be used when those parts are sewn together into a garment. Thus, sewing lines for the garment into which the parts are to be made can be written onto these parts by a printing device which is translated in a manner similar to the manner in which the laser beam is translated and also under the control of the digital computer 21.

Turning next to a more detailed consideration of the optical devices 14 and 15, the function of the first optical device 14 is to bend" the laser beam from its initial direction along the X axis to a second direction along the Y axis. This is accomplished preferably by means of a known optical device called the pentaprism which is operative to receive the initial portion 11a of the laser beam in its collimated (focused at infinity) state and to reflect that beam so that the second portion 11b of the laser beam which leaves the optical device 14 will be at 90 to the first portion 11a, and still collimated. The pentaprism, although known to those skilled in the art, is described in greater detail and shown in the above-referenced application entitled LASER CUTTER OPTICAL SYSTEM of Robert M. Zoot and Douglas W. Wilson. In particular as disclosed in FIG. 3 of that application, the pentaprism is comprised of a pair of flat mirrors disposed at a 45 included angle between them. The incoming laser beam Ila is aimed at one of the mirrors from which it is reflected at the other mirror which it leaves at right angles to its incoming direction. In an actual system wherein the laser beam source 11 was a CO laser model 41 manufactured by the Coherent Radiation Company of Palo Alto, California, generating a 250 watt beam with a diameter of one centimeter, the mirrors comprising the pentaprism were each a 1-% inch diameter silicon substrate coated with a dielectric coating selected for a 10.6 micron wavelength.

It will be understood of course that the pentaprism represents only one type of optical arrangement for changing the direction of the laser beam by 90, several others being also disclosed for sake of example in the Zoot/Wilson application.

Several alternative arrangements may also be utilized for the second optical device 15. Two of these are illustrated in FIGS. 2 and 3. In FIG. 2 the optical assembly 15 is seen to comprise a horizontally oriented focusing lens 45 and a flat mirror 47, inclined 45 to the vertical, both housed in a casing 49 having an inlet window 51 and an outlet window 53. The collimated, redirected laser beam I lb emerging horizontally from the first optical element 14 and entering the second optical device 15 through its inlet window 51, is focused by the focusing device 45 and is changed from its horizontal direction to a final vertical direction aimed at the conveyor work support surface 17 by the inclined mirror 47 through the housing outlet opening 53.

The alternative optical device 15a in FIG. 3, disclosed in detail in the aforementioned Zoot/Wilson application, is comprised ofa housing 55 containing a focusing mirror 57 at one of its ends which receives the collimated laser beam 11b through an inlet opening 59. From the mirror 57 the laser beam is reflected onto a flat mirror 58 which is inclined 45 to the floor of the housing so as to reflect the beam out of the housing 55 through an outlet opening 61. The focal length of the mirror 57 is selected so as to bring the beam reflected therefrom to a focus at the conveyor work support surface 17 or slightly above it, depending upon the thickness of the material which is to be cut. In the abovementioned system which has been built, both of the mirrors 57 and 58 had a one inch diameter and were silicon substrates coated for a 10.6 micron wavelength, with the focusing mirror 57 having a radius of curvature of 12 inches. The distance between the mirrors 57 and 58 was selected to be approximately 3 inches, as was the distance from the mirror 58 to the work support surface 17, giving a beam diameter of approximately one thirty-seconds of an inch where the beam was intercepted by the material lying upon that work support surface.

Yet another possible alternative for the focusing system for the laser beam is disclosed in the abovereferenced U.S. Pat. application Ser. No. 3,627 by Howard R. Friedrich for a LASER LENS COOLING SYSTEM. In that system the positions of the elements 45 and 47 shown in FIG. 2 of the present application are reversed so that the collimated laser beam 11b first strikes a mirror so as to change the beams direction to the vertical, and the vertically downwardly projected final portion of the laser beam is then focused by a focusing lens system having a vertical axis from which it emerges toward and impinges upon the work support surface 17.

One of the important advantages of the system of the present invention is that it permits the cutting of fabric in a single layer. FIG. 4 illustrates how a single layer of fabric may be held upon the work support surface 17 while the by-products of the laser cutting operation are being removed and the ignition of the cut fabric is being inhibited. In accdordance with this aspect of the invention the work support surface 17 presented by the conveyor is air-permeable and air is drawn away from the underside of that surface by means of a chamber 63 which extends under the surface. Air is exhausted from the chamber 63 through an exhaust duct 65 by a conventional exhaust fan (not shown), causing the air pressure under the support surface 17 to be lower than that above it, and air and smoke to be drawn down through the support surface 17 and away from the system. It should be noted that this method of smoke removal and holding down of the material lying on the support surface has certain drawbacks, the principal of which is that some of the by-products of the cutting operation, such as smoke, tend to become lodged in the cut material. Therefore, alternative means may be employed for holding the cloth upon the air-permeable support surface 17 and for removing most of the cutting byproducts generated. One of these disclosed in the above-referenced U.S. Pat. application Ser. No. l84,l39 filed by Castro et al., entitled MATERIAL HOLDING AND SMOKE REMOVAL SYSTEM FOR A LASER CUTTER. In the system disclosed in the referenced application, rather than to draw air directly down through the air-permeable support surface 17, it is caused to flow along and across that surface above it, after which it is redirected so as to flow back across that surface underneath it. In this manner byproducts of the cutting operation, such as smoke, are removed without trying to pull them through the cut material which, moreover is held against the support surface 17 by the pressure differential which exists between the air which flows above the surface and that which flows below it.

Returning to the exemplary environmental control illustrated in FIG. 4, ignition of the fabric which is being cut is controlled by directing a flow of gas through a small pipe 67 at the cutting area 69. The gas may be an inert gas such as nitrogen, in order to extinguish any flames which might be produced. Alternatively it has been found that if air is blown through the pipe 67 at the ignition area 69 at a sufficient velocity, it will extinguish any incipient flames through the same action by which a candle is blown out. To aid in the removal of debris created at the cutting area 69, an additional exhaust pipe 71 may be provided whose inlet is positioned next to the cutting area and from which air is exhausted by conventional means so as to evacuate most of the undesirable debris.

The gas which is to be discharged through thepipe 67 is supplied through an inlet pipe 73 which also serves to pressurize the inside of the housing 66 in which the optical elements are contained and from which the pipe 67 depends. By thus pressuiizing the housing, a continuous airflow can be maintained through the inlet and outlet openings of the housing through which the laser beam enters and exits, ther3by preventing the entry of undesirable debris therethrough. Alternatively, as shownin the refernced Castro et al. application on ENVIRONMENTAL CON- TROL AT LASER CUTTING POINT, air may be caused to flow across the outlet window, through which most of the debris would tend to enter the housing, so as to create an air curtain to prevent contamination of the optics within the housing. It will be understood of course that, whereas the chamber 63 under the movable support surface 17 is stationary, the portions of the environmental control system which are located above the support surface are movable with the optical assembly contained in the housing 66, this applying particularly to the pipes 67, 71 and 73.

DETAILED DESCRIPTION OF THE EXEMPLARY SYSTEM 1. In general Turning next to FIGS. 5, 6 and 7, the physical arrangement of the exemplary cloth cutting and marking system will be described in detail. Referring first to FIG. the principal components of the system include a cutting and printing unti 75 within which those operations take place, a set of servo amplifiers 77 from which the signals controlling the cutting and printing elements emanate, and a control booth 79 in which the operator is seated and which contains the computing elements of the system.

2. The cutting and printing unit a. In general Turning first to a detailed description of the cutting and printing unit 75, it is comprised principally of the conveyor 17, the fabric spreader 43 at one end of the conveyor, a scrap disposal unit 85 shown in dashed line at the opposite end of the conveyor, and two cutting areas 13A and 13B alternating with two printing areas 91A and 91B disposed along the length of the conveor 17 between the spreader and the scrap disposal units 43 and 85.

b. The conveyor The conveyor 17 performs several tasks in the cutting and printing system. When its belt is in motion, it transports fabric from the spreader 43 at one end to, a cut piece pickup area near the opposite end. Additionally, the stationary framework portion of the conveyor 17, including principally a pair of steel beams 95 held by a set of legs 97, provides rigid support for the lasers 11A and 118 a pair of cutting and printing crossarms, the spreader assembly 43 and the scrap disposal unit 85.

In a particular unit proposed for construction, the conveyor assembly including the above-mentioned equipment would be approximately 87 feet long, 9 feet wide and 4-% feet high. The conveyor would provide a level work surface area approximately feet long by 5 16 feet wide located approximately 3 feet above the floor. It will be understood of course that the above figures are mentioned merely to illustrate the magnitude of the appratus shown in FIG. 5 rather than to imply thatthosejfigures are inherently necessary.

The conveyor 17 illustrated in'FIG. 5 is divided into seven functional zones in the-following manner. The spreading function, whereby material is spread onto the support surface formed by the conveyor belt is performed in the first approximately 12 ft. long portion of the conveyor. Apermanently mounted fabric spreader 43 of a typenormally used in apparel cutting rooms occupies the initial 2.5 ft. and the remaining 10 ft. are left unobstructed tohelp in the visual inspection of the un- -rolled fabric for flaws or creases. The cutting and printing zones 13A, 13B, 91A and 918 would each be 10 ft. long in the proposed machine and, for reasons which will be explained hereinafter, would be separated by a 5 ft. buffer zone 98. The last five zones 91A, 13A, 98, 91B, and 138, which in the proposed machine would comprise a 45 ft. long section of the conveyor 17, are dimensionally critical because of the limited focal length of the optics used to focus the laser beam upon the material which is supported by the conveyor. Particular attention should therefore be given to assign fabrication tolerances which will assure the necessary flatness over the entire 45 ft. long area to maintain the material held by the conveyor 17 within the focused portion of the laser beam.

The sixth functional zone of the conveyor 17 is a pick-up zone which in the proposed machine would be approximately2l ft. long and which is left unobstructed to permit access for either manual or automatic piece part pick-up. Part of this pick-up zone is cut away in FIG. 5 to reduce the size of the drawing. Finally, the remaining few inches of level surface between the pick-up zone 90 and the end of the conveyor 17 falls within the operating zone of the scrap disposal apparatus indicated at 85. Not shown in FIG. 5 is the chamber 63 of FIG. 4 which encloses the underside of the conveyor 17 at least in the cutting areas 13A, 1313.

Turning next to some of the details of the conveyor 17, it is comprised principally of a plurality of long and slender slats 99, one of which is illustrated in part in FIG. 6. The use of such slats featuring a honeycomb panel 101 is not applicants invention. Instead the concept of the honeycomb panel itself as a suitable support surface to withstand a focused laser beam is the invention of Robert M. Zoot by whom the above-referenced US. Pat. application Ser. No. 3,665 was filed thereon. Furthermore, the concept of configuring a conveyor out of a plurality of slender slats made of the Zoot-type honeycomb is the invention of Georgette S. Egan, applicant in the above referenced application.

As shown in FIG. 6, the honeycomb slat may be constructed by providing a strip of honeycomb material 101 supported upon a casting 103, preferably aluminum, held rigid by tensioning rods 105. The slats are interconnected into a conveyor belt by means of chains (not shown) attached to their corresponding ends 109. Alternatively, the honeycomb slats may be made lighter by dispensing with the aluminum casting 103 and the tensioning rods 105 and by bonding instead a pair of thin support members to the opposite longitudianl edges of the honeycomb panel 101, with the top edges of the support members being beveled to a knife edge to prevent undesirable reflections from them. Such a honeycomb slat is disclosed and claimed in the abovereferenced Egan application.

Subject to control signals from the control booth 79, the conveyor slats 99 are moved by their connecting chains as a single conveyor belt by a drive motor (not shown) through conventional coupling gears and sprockets. To help the conveyor slats 99 to move smoothly along the steel beams 95, they are provided at their four corners with plastic (typically DELRIN) pads 110 which slide along the suitably finished top surfaces of the beams. Preferably the support beams 95 will have precisely machined surfces covered by a lubricant to minimize friction and wear while also insuring that the slats which ride on them will form a precisely level work support surface. In this connection it is important to give attention to maintaining the sag of the individual slats 99 within acceptable limits dictated by the depth of focus of the laser beam.

c. The spreader Cloth to be supported and transported by the conveyor 17 is dispensed from the fabric spreader 43 which is anchored at the upstream end of the conveyor and on which a bolt of fabric 1 11 is rotatably supported on a frame 113. It will be noted that the spreader 43 is shown to have a set of wheels at the bottom of its frame 113. This is so because the spreader which has been proposed for use in the exemplary system of FIG. 5 is one of conventional construction whose manner of operation is that the entire spreader is moved along its wheels along a level surface onto which the material resting upon the spreader is unrolled as the spreader is moving along. The functions of the fabric spreader 43 and of the material holding surfce 17 in the exemplary system of FIG. 5 are reversed, with the fabric spreader remaining stationary and the work support surface moving, thereby drawing the fabric away from the spreader. This concept of reversing the functions of spreader and work support surface is also the invention of Georgette S. Egan and is separately claimed in her abovereferenced application.

As disclosed more fully in the Egan application, a CRA Champion model spreader is modified by removing a gear with which that model senses the rate of spreader travel along the material support surface. The sensing gear normally drives a shaft on the spreader, and control devices on the latter turn the bolt 11] at a rate which will dispense cloth therefrom at a constant linear rate. As part of the proposed modification this sahft is coupled by an appropriately proportioned drive train to one of the sprockets driving the conveyor belt. By proper gear ratio selection, the bolt lll upon the stationary spreader 43 is caused to feed cloth onto the conveyor belt at the same linear rate at which that belt travels.

Alternatively, as disclosed in the above-referenced Castro, Toscano, Newton application on TENSION- FREE CLOTH DISPENSING APPARATUS, the spreader may be controlled by introducing a freehanging loop into the material between the spreader 43 and the conveyor belt. The length of the loop is sensed by photocells so that bolt 111 is turned in response to the loop becoming shorter than a predetermined minimum.

TI-IE CROSSARM ASSEMBLY Returning now to the cutting and printing unit 75, as mentioned earlier it includes a pair of cutting areas 13A and 13B alternating with a pair of printing areas 91A and 91B. Referring both to FIGS. 5 and 7, the first area through which cloth from the bolt 111 moves is the printing area 91A within which a printer crossarm assembly 127 operates to move a printing element anywhere within the printing area. A similar cutter crossarm assembly 127 moves within the first cutting area 13A just next to the printing area 91A. Since all of the crossarm assemblies are essentially identical whether they carry a cutting head or a printing head, they will all be identified by the reference numeral 127. Moreover, for sake of brevity, in the following discussion of a cutter crossarm assembly 127 shown in FIG. 7 it will be referred to by the abbreviated name crossarm assembly.

The function of the FIG. 7 crossarm assembly 127 is to transport a pair of optical elements, such as the elements 14 and 15 of FIG. 1, within the cutting area 13 along the X direction so that the first optical element 14 remains in the path of the laser beams collimated first path portion 11a. In addition to the crossarm assembly 127 also serves to transport the second optical element 15 relative to the first, along the Y axis so that the element 15 remains in the path of the laser beams collimated second path portion 11b. This is accomplished in the exemplary system of FIG. 5 by aiming the laser beam precisely parallel to the longitudinal (X) axis of the conveyor 17 and moving the first optical element l4 precisely in line with the laser beam so aimed. The first optical element 14 is then made operative to redirect the laser beam exactly from its initial direction so that it becomes projected in the Y direction across the width of the conveyor 17 and across the width of the cutting area 13.

Spanning the width of the conveyor 17, the crossarm assembly 127 has a relatively broad base 128 at one end which rides along a supporting rail 129 mounted upon the steel beam 95. Extending from the crossarm base 128 is a crossarm 131 held rigid by a pair of braces 133 and supported at its opposite end upon a second supporting rail 135 mounted upon the beam on that side, the tip of the crossarm 131 being supported upon the rail by means of a sliding bracket 137.

The crossarm assembly 127 is driven along the X axis by means of an electric motor 139 through a belt 141 which is coupled to and rotates a lead screw 143 extending along the top of the guide rail 129. Also extending along the supporting rail 129 next to the lead screw 143 is a way 145 upon which the crossarm base 128 is guided by a pair of bushings 146 rigidly attached to the base 128 and riding on the way 145. The first optical assembly 14 (FIG. 1) is mounted near the crossarm base 128 so as to move therewith along the X axis in the path of the first portion of the laser beam. An appropriate mounting place is indicated in FIG. 7 by the block 148, with the first optical assembly 14 being omitted for sake of clarity. The second optical assembly 15 (FIG. 1) is mounted on a second block 150 which is actually a carriage movable toward or away from the first mounting block 148 so as to maintain the optical assembly 15 (not shown in FIG. 7 for sake of clarity) in the path of the laser beam emanating from the first optical assembly 14 carried by the first block 148.

The carriage 150 is transported along the crossarm 131 by means of a Y axis electric motor 149 through a belt 151 and through a lead screw 153 which extends the length of the crossarm 131. A Y axis way 155 is also provided next to the lead screw 153 to help guide the carriage 150. The position of the carriage 150 along the crossarm 131 is monitored by means of a resolver 157 mounted at the tip of the crossarm 131 and geared to the lead screw 153. A similar resolver (not shown) may be geared .to the X axis lead screw 143 to monitor the crossarm position along that axis.

To implement the concept of smoke removal illustrated schematically in FIG. 4 an air scoop 159 is provided inside the carriage 150 and is connected by means of a coupling 16] to an air duct 163 which runs along and above the crossarm 131 and whose top face is air-permeable to permit communication with the coupling 161. The duct 163 is connected at one of its ends through a further coupling 167 to a second duct which runs along the X axis supporting rail 129 under the crossarm base 128. Air is exhausted from one end of the second air duct 165. Both of the couplings 161 and 167 are sliclable along the tops of their respective ducts 163 and 165 so that a continuous airflow is maintained through the system away from the scoop 159 inside the carriage 150.

The printer crossarm assembly 127 for transporting a printing unit within the printing area 93 is identical to the crossarm assembly 127 illustrated in FIG. 7, except that the smoke removal components are omitted and of course it carries no optical elements. Instead it carries a printing device of conventional construction upon its transport carriage 169. Also to take best advantage of the available space, the base portion of the printer crossarm assembly 127 is on the oppositeside of the conveyor 17 from the base portion of the crossarm assembly 127. A suitable printer to be carried by the carrier 169 is marketed by the A. B. Dick Company under the name of VIDEO JET. The VIDEO JET operates like a miniature fluid nozzle, dispensing a uniform ink stream from a nozzle tip. The nozzle is modulated electro-mechanically at a high frequency to break the ink stream into uniform droplets and the ink stream is modulated electrically to deflect the particulated ink stream as a function of an electric charge imparted to it. For the exemplary system of FIG. the nozzle assembly would be used without modulating either the ink stream or the nozzle. Instead a continuous stream would be dispsensed, with printing being accomplished by moving the carriage 169 along the X and Y axes to permit character generation as well as the drawing of any type of guide line. When a no-print condition exists, which is usually most of the time, the ink stream would be deflected into a gutter (not shown) from which it would be returned to the ink reservoir, thereby reducing ink consumption to about one-sixtieth of a quart per hour for the VIDEO JET printer. Filtering of the circulated ink in the high lint environment which is to be expectedwill be a critical requirement to which careful attention will have to be paid.

The crossarmmethod of traversing the cutting and printing units was developed under applicants direction. In a system subsequently built by others for the assignee of the present invention, a different mechanism was employed which may be preferable in some applications where high speed and low inertia are controlling considerations. This mechanism was manufactured I by Xynetics Inc. of Canoga Park, California and is described in Sawyer US. Pat. No. 3,376,578. Briefly, a platen containing a grid of magnetic material is mounted over each cutting or printing area. In the cutting areas 13A and 138 a pair of linear motors are carried on the underside of each platen upon which they are stepped digitally in the X and Y directions. To perform the function ofa crossarm 127 the two motors are moved on common X coordinates along the Y axis. The first of them travels along the outer edge of the cutting area 13 and carries the first optical element 14. The second linear motor carries the second optical element 15 and moves not only along the Y axis with the first motor, but also moves relative to it along the X axis, just as the crossarm carriage 147 travels relative to the mounting block 148. In the cutting areas 91 only the second linear motor is required, carrying the printing unit along the X and Y axes.

A cloth panel cut by means of the exemplary system of FIG. 5 is illustrated in FIG. 8. The panel is seen to be cut in accordance with a pattern in a series of straight line segments 170, the starting and stopping points 172 of which are denoted by small circles. The number of line segments 170 and their length are selectedso that the maximum deviation of the cut piece from the actual pattern will be less than, or equal to, a specified tolerance. In the proposed system this tolerance was specified as 0.0625 inches. 1

FIG. 9 serves to explain a source of error which tends to occur in executing a pattern such as that shown in FIG. 8, this error being inherent in a type of servomechanism which may be used to advance the second optical element 15, hereinafter referred to as the cutting head," in the X and Y directions with the crossarm assembly 127. If the servomechanism used is of a type having an appreciable velocity following error, the element which is being moved by the servomechanisms in the X and Y directions will lag in actual position the position where it is commanded to be at any given instant by the signals being fed to the servomechanisms. As shown in FIG. 9 for example, the first path segment extends from a starting point 171 to a terminal point 173 from which the second segment extends toward the right to a point 175. Because of the following error, the commanded element such as the cutting head 15 will fall short of its commanded position 173 at time T1 and will only be at point 177. Consequently, to permit the commanded component to move toward its desired position 173, a dwell time AT is provided before the next motion command is applied to the servomechanism.

Moreover, because there is a permissible error E which represents the distance by which the commanded element may miss its commanded point 173, the dwell time AT need not be made long enough to permit the element to move all the way to its commanded point 173 but may instead be terminated before that time, and the next command may be applied to it at time T2, which in the illustrated example is a purely X command, causing the commanded element to veer toward its second target point 175 such that it misses the first commanded target point 173 by a distance E. Stating it differently, in the exemplary system illustrated in FIG. 5 the acceleration and deceleration at the ends of the programmed line segments are also programmed. This acceleration/deceleration function is implemented by including a dwell time command as part of each control tape data block, wherein each block represents a series of movements to be executed by the crossarms 127 during an operating period. The dwell time or time delay at the end of each line segment 170 will be computed by the crossarm computer 21 as a function of four variables: Line segment length, initial velocity of the cutting head at the start of the line segment, allowable cutting tolerance E, and turning angle of the cutting head from a given line segment to the next.

To execute the movement illustrated in FIG. 9 the cutting head would be programmed for a combined X axis and Y axis displacement, taking it from the point 171 to the point 173 through axis components X1 and Y1, representing one straight line segment 170. This would be followed by a dwell time for that same line segment I70, starting at T1 and ending at T2. The dwell time command would be followed by a programmed X axis displacement, representing movement to execute the next straight line segment 170 from the point 173 to the point 175 through a distance X2. As will be explained hereinafter, although the commands as received from the production tape 25 (FIG. 1) are incremental displacements, these commands are converted in the digital computer 21 and the positioning electronics 19 of the system into synchronized X and Y axis servo velocity commands, typically a series of pulses. For example, the commanded displacement X1 would be converted to a constant velocity for a time T1. At time T1 the X axis velocity command goes to zero but because of the velocity following error, the X axis position at this time is only XTl. The conclusion of the velocity command at time T1 coincides with the beginning of the dwell time AT. During this time the movement along the X axis decelerates and the position at the end of the dwell time AT is XT2. However, since neither the X axis position nor the Y axis position is required to go to the ideal end point 173, the next position command X2 may be issued at this time T2. Thus the velocity command corresponding to the next incremental distance X2, representing the distance along the X axis between the points 173 and 175 may be issued to be executed during the time period which begins at T2 and ends at T3. The length of the dwell time AT is computed so that the total error E will be less than or equal to the maximum permissible error, assumed previously as 0.0625.

It should be understood that the only reason for delving into this aspect of servomechanism design is because in the following detailed description ofa suitable electronic circuit for driving the servomechanisms, provision is made to insert a dwell time at the end of each path segment, so as to minimize the following error inherent in the servomechanisms that are described herein. However, there are other types of servomechanisms such as that described in the abovereferenced Sawyer patent, which do not have the velocity following error that necessitates the provision of a programmed dwell time and to which the explanation given with reference to FIG. 9 would be irrelevant.

3. Crossarm Allocation of Marker Segments a. In general Summarizing what has been described thus far, the exemplary cutting and printing system of FIG. 5 features a pair of cutting areas 13A and 138, each of which contains a separate cutting device, a pair of cutting areas 91A and 918 containing respective printing devices. The use of two separate cutters sharing a common computer 21 represents a preferred embodiment of the invention. What will be described next is a particularly advantageous organization of the elments of the system of FIG. 5 whereby the cutting workload may be divided between the cutting heads 15 in the cutting areas 13A and 138 in a straightforward manner. Yet, by virtue of the system organization which will be described, the cutters between them will cut every re quired part without getting in each others way. This particular aspect of the system is not the invention of Applicants, but is the invention of Robert L. Hasslinger by whom the above-referenced patent application for WORKLOAD ALLOCATION FOR ONE OR MORE TOOLS has been filed. Because the respective tools in the exemplary system of FIG. 5 are laser cutting heads carried by respective crossarms 127, the workload allocation concept will be referred to hereinafter as crossarm allocation.

b. Detailed discussion of producing a cutting sequence tape Before explaining crossarm allocation in detail, it will be helpful to summarize the manner in which one would generate and store the data representing the patterns according to which garment parts are to be cut by the system from a layer of fabric. A portion of a length of fabric from which parts are to be cut for a garment is shown in FIG. 11. Typically, fabric is divided into lengths of the order of 30 ft. and the parts for up to three suits are cut from that length of fabric. Generally, the patterns corresponding to the various parts which are to be cut are laid out by people who are skilled in so arranging the patterns as to leave a minimum of space between them, thus minimizing fabric wastage. It is a portion of such a layout that is shown in FIG. 11 which contains most of the parts for a mans suit. Thus the trouser parts are discernible along the top of the material 179 in FIG. 11, and the panels 181 for a mans jacket are seen at the lower right-hand corner thereof.

The portion illustrated in FIG. 11 represents approximately one third of a 30 ft. length of fabric, the collection of patterns representing the parts to be cut from that length of fabric being commonly referred to as a marker." In the exemplary system the electrical signals digitally representing the patterns according to which parts are to be out are stored on a roll of magnetic tape, referred to herein as the cutting sequence tape 25. The cutting sequence tape is compiled through a series of steps which involves generally (1) the designing of a garment, (2) the conversion of each part of that garment into digital signals representing the pattern for those parts by means of a digitizer, (3) the production of a pattern tape containing digital signals representing the digitized patterns, (4) the production of a marker tape containing the relative positions of the patterns making up the garment and perhaps those making up an additional garment as well) and the combination of the contents of the marker tape and the pattern tape into the final cutting sequence tape 25.

Referring to FIG. 12, the first of the above steps is performed by an artist who designs a new garment and produces a drawing thereof. From that drawing a set of average-size patterns are produced as well as a set of graded patterns for all additional smaller and larger sizes. All of the patterns 183 are then placed on a digitizer 185 which is a commercially available device having a large flat surface upon which the pattern is placed and a follower device which can be traced along the perimeter of the pattern. By means of transducers and electronic circuits the digitizer converts the successive physical positions of its follower into digital signals repreenting the X and Y coordinates the successive positions of the follower and therefore the perimeter of the pattern.

In addition to producing a description of the pattern perimeter, the digitizer is used to provide three other types of data. These include: (1) a description of the particular part; (2) a location key; and (3) an alternate origin point. The meaning of the location key and of the alternate origin point will be better understood by referring again to FIG. 11, and to the trouser part 180 illustrated therein. For each pattern the location key consists of three points 187, 189 and 191. The first point 187 is located at the lower left-hand corner of the part, called the origin." The second point 189 is located at the right end of the part at the same Y coordinate as the point 187 but at a different X coordinate. The third point 191 of the location key is directly above the second point 189, at the same X coordinate but at a different Y coordinate. By defining the location of the key of a given pattern, that is by defining the location of its three points 187, 189 and 191, the location and orientation of the entire pattern is unambiguously defined. Thus, each ofthe parts as shown in FIG. 11 has a key whose desired location relative to every other part on the fabric 179 is stored in a manner to be explained.

Diagonally opposite from the first (origin) key point 187 is the alternate origin 193 of the part and of its corresponding pattern. By providing an alternate origin for the part it is possible to begin cutting it from that point rather than from the origin point 187 which may yield a shorter path length between that pattern and the next pattern to be cut, this path length being referred to as a dry haul.

The description of each pattern is produced by means of a typewriter keyboard associated with the digitizer, by means of which numbers or letters, or a combination of both, may be entered into the storage medium upon which the position information is stored by the digitizer, these characters serving to identify the particular pattern which has been digitized.

The next step is to produce a pattern tape 195 which contains the digitized patterns for a given garment model, arranged so that any parttern can be read from the tape by referring to the part number of that pattern. Additionally it is desirable that the data on the tape be in a language or form compatible with a digital plotter so as to permit the patterns on the tape to be plotted 18 for checking purposes. In the process of producing the pattern tape 195, the digitized data produced by the digitizer is processed on a general purpose computer such as the IBM 1130 wherein the data is converted into a plotter-compatible language and is also edited to uncover any errors which might have been introduced during the digitizing process.

From the edited pattern tape 195 or directly from the digitizer the digitized pattern signals are applied to a plotter 197 by means of which one-fourth scale patterns 199 are drawn. These one-fourth size patterns are then laid out on a sheet of paper into the most compact configuration, such as that shown in FIG. 11. This step is usually done manually. The resulting one-fourth size marker 211 is then placed on a digitizer 213 which may be of the same type as the digitizer 185 referred to earlier, and by means of the digitizer 213 several types of data are derived from the marker 211. These include: I

(a) identification of the pattern part; (b) identification of the marker containing the pattern; and (c) location of the pattern key. The data generated by the digitizer is then edited by means of the same computer used to edit the pattern data. This serves both to convert the digitizer-generated data into plotter-compatible language and to uncover errors introduced during the digitizing process. The resulting edited data is stored on a magnetic tape labelled Edited Markers 215 in FIG. 12, which contains the precise locations of all patterns comprising the whole marker as well as the identification legent for each part of the marker. At this point the edited marker and pattern tapes 215 and are placed into a marker library 217 and a pattern library 219 respectively. Also at this time a marker catalog 221 is printed from the marker tape 215 which includes identification of the marker, its number, its maximum X and Y dimensions and its size. A pattern catalog 223 is also printed, it containing the number of each pattern and the number of the model of which it is a part.

Using the marker catalog 221, the pattern catalog 223, information concerning plant capacity 225, customer orders 227 for particular garments, and piece goods in stock 229, a production schedule determination 224 is made. The production schedule determination 224 is recorded on a work order sheet on which the scheduler notes both the number of the markers which contain the desired patterns and the material from which the parts for the ordered garments are to be cut. Preferably customer orders for garments will be arranged so that each customers order will be completed before the next customers order is cut.

To facilitate processing of the work order sheet, it is key-punched onto cards acceptable by a general purpose computer such as the IBM 360/30. The keypunched work order is then applied as the input to such a general purpose computer which is next used to compile the cutting sequence tape 25 therefrom. The process whereby the contents of the work order sheets are transformed into the cutting sequence tape 25 will typically include more than one processing run by the computer. During the initial run a production schedule sequence tape 231 is generated, this tape containing in proper order the identities of all markers required to fill the orders on the work sheets. As part of this run the computer may also verify that the required markers are indeed in the marker tape library 217. From the production schedule sequence taper 231 the computer will produce a marker sequence tape (not indicated in FIG. 

1. A severing system comprising in combination: a. means for maintaining a radiant energy beam focused in a cutting plane within a cutting area; b. endless means, including air-permeable means substantially non-reflecting to said radiant energy beam for supporting material thereon in at least a single flat layer; c. means for moving said supporting means with said material thereon through said cutting area, with said material lying flat upon said supporting means substantially in said cutting plane within said cutting area; d. means for traversing said focused radiant energy beam, while it is focused in said plane, along a predetermined route over said work support surface within said cutting area which route includes a plurality of separate, spaced apart closed patterns so as to sever from said material along said route a plurality of parts conforming to said closed patterns; and e. means for interrupting said radiant energy beam when it is between said patterns.
 2. A severing system in accordance with claim 1 characterized further in that said radiant energy beam is a laser beam.
 3. A severing system in accordance with claim 2 characterized further by means for forcing gas to flow away from the underside of said air-permeable means so as to remove by-products produced by said severing.
 4. The severing system of claim 2 characterized further in that said means for traversing includes a numerical control unit responsive to stored command signals representing points along said route.
 5. A severing system comprising in combination: a. means for maintaining a radiant energy beam focused in a cutting plane within a cutting area; b. endless means including air-permeable means for supporting material thereon in at least a single flat layer and substantially non-reflective to said radiant energy beam; c. means for moving said supporting means with said material thereon through said cutting area, with said material lying flat upon said supporting means substantially in said cutting plane within said cutting area; d. means for traversing said beam, while it is focused in said plane, along a predetermined route over said work support surface within said cutting area which route includes a plurality of separate, spaced apart parts conforming to preselected closed patterns so as to sever said material along said route, thereby cutting said parts out of said material in said cutting area according to said patterns; and e. means for forcing gas to flow away from the underside of said air-permeable support means so as to remove by-products produced by said severing.
 6. A severing system comprising in combination: a. stationary means for generating a beam of coherent radiation; b. movable means for focusing a beam of coherent radiation rEceived thereby in a cutting plane within a cutting area; c. endless means including means substantially totally transmissive to said coherent radiation for supporting material substantially in said cutting plane in at least a single flat layer; d. means for moving said movable focusing means within said cutting area in a second plane parallel to said cutting plane; e. means for projecting said beam from said stationary means onto said focusing means during all of its positions in said cutting area; f. means for moving said supporting means with said material thereon through said cutting area, with said material lying flat upon said supporting means substantially in said cutting plane within said cutting area; and g. means for commanding said moving means to move said focusing means along a predetermined route in said second plane so as to burn a corresponding route into and through the material lying on said supporting means in said cutting plane within said cutting area.
 7. A system for severing patterns through a layer of material in accordance with stored signals representing the locations and perimeters of said patterns on said material comprising in combination: a. means for projecting a focused beam of coherent radiation at any desired point within a cutting area; b. endless conveying means for progressively advancing a layer of material into said cutting area and including air-permeable means for fully supporting said material therein flat and motionless, after each advancement thereof; and c. digital computing means for controlling said projecting means to move said focused beam over said air transmissive means within said cutting area in accordance with said stored signals after each advancement of said material into said cutting area, thereby severing said patterns through said material.
 8. A system in accordance with claim 7 characterized further in that: a. said projecting means includes a stationary laser beam source, movable means for focusing said beam onto said cutting plane and digital servo means for traversing said movable means along said cutting plane in response to a pair of velocity-representative pulse trains; and b. said digital computing means is programmed to derive said pulse trains from said stored signals.
 9. A system in accordance with claim 7 and characterized further in that said conveying means is controlled by said computer to advance after the signals representing a predetermined group of said patterns have been executed by said projecting means.
 10. A system according to claim 7 and characterized further by printing means movable under the control of said computer in response to additional stored signals for marking said material.
 11. A system for producing, from a layer of material parts conforming to preselected patterns and marked with information comprising in combination: a. means for storing signals digitally representing the periphery of each said pattern, the information to be marked on the part conforming to said pattern, and the desired locations of said parts relative to each other in said material; b. means for cutting movable within a cutting area; c. means for printing movable within a printing area separate from said cutting area; d. endless, air-permeable conveying means for advancing a layer of material through said cutting and printing areas in succession so as to stop successive portions of said material in said cutting and printing areas; and e. computing means for controlling said cutting and printing means to execute cutting and printing paths upon said material concurrently in accordance with said stored signals after each stop of said conveying means.
 12. The system of claim 11 characterized further in that said conveying means is a conveyor having an elongate flat work support surface, said cutting and printing areas form rectangular areas through which said conveyor moves, and in that there is additionally provided for eAch of said movable cutting and printing means a carriage movable in a plane parallel to said work support surface respective ones of said cutting and printing means being mounted on, and carried parallel to said work support surface by, respective ones of said carriages.
 13. The system of claim 11 characterized further in that said conveying means moves so as to advance said layer of material first through said printing area and then through said cutting area, whereby printing paths are executed prior to cutting paths on respective ones of said successive portions of said material.
 14. A severing system comprising in combination: a. means for maintaining a laser beam focused in a cutting plane within a cutting area; b. an endless conveyor including air-permeable means substantially non-reflecting to said laser beam for supporting material thereon in at least a single flat layer; c. means for progressively advancing said supporting means with said material thereon through said cutting area in steps, with said material lying flat upon said supporting means and having successive portions thereof brought to a stop substantially in said cutting plane within said cutting area; d. means responsive to stored control signals for traversing said focused laser beam, while it is focused in said plane and after a given portion of said material has been brought to a stop within said cutting area, along a predetermined route over said work support surface within said cutting area, which route includes a plurality of separate, spaced apart closed patterns so as to sever from said material along said route a plurality of parts conforming to said closed patterns; and e. means for interrupting said laser beam when it is between said patterns.
 15. A severing system in accordance with claim 14 characterized further in that said means responsive to stored control signals includes a computer and a numerical control unit operatively coupled thereto and in that said computer is connected to said means for progressively advancing said supporting means and is operative to cause said last means to start a given one of its steps after said laser beam has been traversed over its predetermined route, said computer also being connected to said means for interrupting said laser beam and being responsive to stored control signals to start and stop said means for interrupting said laser beam. 